This invention relates generally to nuclear reactors and more particularly to a heat removal system in a containment.
One known boiling water nuclear reactor includes a reactor pressure vessel (RPV) positioned in a drywell, or containment, suppression pool (SP) and a passive containment cooling system (PCCS). The RPV contains a core, and the containment is designed to withstand design pressure defined by a loss of coolant accident (LOCA) and other loads associated with plant operation. The PCCS is configured to limit the containment pressure below the design value and to keep the RPV core substantially cool during a postulated loss of coolant accident.
Typically the bottom floor of the containment vessel is part of the basemat of the reactor building. The basemat, in certain situations, rests on bedrock and typically supports the reactor building, containment vessel wall, suppression pool and reactor pedestal that supports the RPV including the internal components of the reactor. In the event of a severe accident in which the molten core is postulated to penetrate the lower head of the reactor, the molten core would flow into the region below the reactor pressure vessel and contacts the floor of the containment vessel that is lined with a stainless steel liner. There are several known methods of protecting the containment liner and basemat structure from the molten core debris. However, some methods do not include long-term stabilization by cooling the molten core debris.